Figure 2

Sequence of events that leads from SU-5416-induced VEGF blockade to the increased growth of VSMC. VEGF receptor blockade induces apoptosis of vascular endothelial cells. Apoptotic endothelial cells release growth factors such as VEGF and TGF-β₁, and, whereas VEGF inhibits apoptosis, TGF-β₁ promotes VSMC proliferation. Definition of abbreviations: HPMVEC = human pulmonary microvascular endothelial cell; VSMC = vascular smooth muscle cell; TGF-β₁ = transforming growth factor-β₁; VEGF = vascular endothelial growth factor; SU5416 = a combined VEGF I and II receptor blocker.